About GNU/Linux

This article simply explains how to get two same screens with a same computer. We're going to use xrandr, the soft is normally already installad on your system.

Assumptions ; you have a laptop (or desktop) with one screen, and you would like to add a second screen showing the same things. Everything can be done as user.

Let's get information about your laptop's screen :

xrandr

Here is the output :

$ xrandr 
Screen 0: minimum 320 x 200, current 1280 x 1024, maximum 1600 x 1600
VGA disconnected (normal left inverted right x axis y axis) 338mm x 270mm
LVDS connected 1280x800+0+0 (normal left inverted right x axis y axis) 331mm x 207mm
  1280x800       60.0*+   60.0  
  1280x768       60.0  
  1024x768       60.0  
  800x600        60.3  
  640x480        59.9  
TV disconnected (normal left inverted right x axis y axis)

LVDS ; this is the laptopt's screen.
VGA ; this will be your second screen.

Let's add the second screen :

We're going to add the second screen. The first and the second screen don't have the same resolution (in my case), I must give two different resolutions to each screen. Note you can only give the resolutions you get with "xrandr". One command is sufficient :

xrandr --output VGA --mode 1280x1024 --output LVSD --mode 1280x768

Let's split the command :

--output VGA --mode 1280x1024

This gives the resolution of the second screen.

 --output LVSD --mode 1280x768

This gives the resolution of the laptop's screen.

Add resolutions :

If the resolution you want is unavailable, you must add a mode, read this article.

Disconnect a screen :

If you don't want to use the laptop's screen ;

xrandr --output VGA --mode 1280x1024 --output LVDS --off

And for the second screen :

xrandr --output LVDS --mode 1280x768 --output VGA --off

GUI :

A GUI exists to manage your screens : lxrandr.